Sound-reproducing mechanism



Patented Apr. 7, 1931 PERCY A. ROBBINS, F HIGHLAND PARK, ILLINOIS soumJ-Rnrnonuome mncneivrsu Application filed May 17,

In my co-pending application No. 363,951,

of even date herewlth, I disclosed means for reproducing sound utilizing an undulating sound trace on a moving strip to shift a magnetic flux laterally of the strip to thus cut the turns of an electric conductor to induce a current therein varying similarly to the undulations of the sound trace.

My object in the present application is to devise means for similarly inducing an electric current utilizing a sound trace adapted to shift the magnetic flux lengthwise of the stri I httain my object by producing a concentrated magnetic field through which is moved a strip havin a sound trace formed thereon adapted to shlft the magnetic flux longitudinally of the stri as the latter moves through the magnetic fie d. A coil, having its turns at one side parallel to the surface of the strip and extending transversely of the strip through the magnetic field, has an undulatory current induced therein as the magnetic flux is shifted back and forth.

The invention is hereinafter more fully described and is 'illustarted in the accompanying drawings in which Fig. 1 is a side elevation of apparatus constructed in accordance with my invention;

Figs. 2,3, 4 and 5 side elevations of part of the same showing the distortion of the magnetic field due to the passage of the sound record;

Fig. 6 a plan view of part of a. sound record adapted for use with my invention; and Fig. 7 a plan view of the sound record illustrated in Figs. 1 to 5.

- Referring particularly to Fi 6, 1 is a flexible strip of material such, fbr example, as used in kinematographic apparatus which usually, when the device is used in connection with such apparatus, will bear a series of pictures. On this strip is formed a sound trace 2, usually by the application of paramagnetic material thereto. This sound trace may take any known form provided there is a difference in the distribution of the material lengthwise of the film which will dietort a magnetic field through which the strip 50 may be passed in a direction lengthwise of lengthwise through the -ma 1939. Serial No. 868,952.

the strip. .Such atrace is illustrated diagrammatically in the drawing.

Referring particularly to Figs. 1 to 5 of the drawin s, 3 is an electro-ma net referably formed with pole pieces Io e edge form, the pole pieces being located close together at opposite sides of the strip 1. A

coil" of wire 4Jis. secured-by a clamp 5 to an arm 6 pivotally mounted at 7 on a stationary.part.8," which is shown as secured to the pole pieceofsthe magnet 3. A worm and uadrant adjustment 9 is provided whereb t e arm 6 may be adjusted to vary the position of the coililengthwise of the strip 1. The clamp '5 provides' me'ans for adjusting the coil in a'direction perpendicular to'the strip. 7 Figs. 2 to 5 of the drawin 3 show diagrammatically how the lines of orce in the magnetic field are shifted by the passage of. the

("sound trace. These lines of "force moving relative-to the turns of the coil 4 generate an undulatory' electriccurrent in said conductor which may be suitably-amplified and reproduced assound, waves.

The intensity of the currents induced in the coil twill depend upon the intensity of the disturbance of, the position of the mag netic flux by the sound trace.

' What I claim is:

" 1. Sound reproducing apparatus comprising a magnet having its poles positioned; close to one another; a strip adapted to move etic field between the poles, said strip aving a paramagnetic sound trace formed thereon adapted, as the strip moves, to shift the magnetic flux back and forth lengthwise of the stri and a coil having its turns-at one side para el to the surface of the strip and extending transversely of the strip t r netic field, so that a current will be induced therein b the movements of the magnetic flux relative thereto.

2. Sound reproducing apparatus comprising a magnet having its poles positioned close to one another; a strip adapted to move lengthwise through the magnetic field between the poles, said strip having a paramagnetic sound trace formed thereon adapted, as the strip moves, to shift the magnetic flux ough' the mag back and forth lengthwise of the stri a coil having its turns at one side paralle to the surface of the strip and extending transversely of the strip throu h the magnetic 5 field, so that a current will e induced therein by the movements of the magnetic flux relative thereto; and means for ad] ustin'g the olstion of the coil relative to the magnetic e t 3. Sound reproducing apparatus comprising a magnet having its pole faces parallel and positioned close together; a ribbon of non-magnetic material designed to move len hwise of itself through the magnetic fiel between the pole faces, said ribbon having a sound trace of paramagnetic material formed thereon, said sound trace providingla series of paramagnetic markings along t e length of the ribbonada ted to vibrate the magnetic flux back and orth len hwise of the ribbon as the ribbon moves; an a coil inductively related to the magnetic field and having its turns at one side parallel to the surface=o f ,the ribbon and extending transversely of the ribbon through the magnetic field, so that a current of electricity will be induced therein by the movements of the magnetic flux relative thereto.

4. Soundreproducing apparatus comprisso ing a magnet having its pole faces parallel and positioned close together; a ribbon of non-magnetic material designed to move lengthwise of itself through the magnetic field between the pole faces, said ribbon having a sound trace of paramagnetic material formed thereon, said sound trace providingla series of parama etic markings along t e length of the rib on adagpted to vibrate the magnetic flux back and orth lengthwise of the ribbon as the ribbon moves a coil inductively related to the magnetic field and having v its turns at one side parallel to the surface ofthe ribbon and extending transversely of the ribbon through the magneticfi'eld, so that a current of electricity will be induced there- Y in by the movements of'the magnetic flux relative thereto; and means for admsting the olstion of the coil relative to the magnetic e Si ed at Highland Park, 111., this 6th day of ay, 1929.

PERCY A. ROBBINS. 

